1. Field of the Invention
The present invention relates to a system and method for predicting radio wave propagation characteristics, and in particular to a system for predicting the radio wave propagation characteristics by a technique of geometrical optics employing a so-called ray launching processing.
2. Description of the Related Art
A radio wave propagation simulator is employed to assist an arrangement of a base station or a host system in a radio communications system. The received power or delay spreading at any receiving point is assessed by using the radio wave propagation simulator to determine an suitable installation site of a transmitting station, so that the overall efficiency can be enhanced by reducing the number of base stations to be arranged.
The radio wave propagation simulation is largely classified into a statistical technique and a deterministic technique. The statistical technique gives an expression for estimating the propagation loss with the arguments of distance and frequency to determine the parameters on the basis of a large amount of data resulted from actual measurements of the propagation loss in accordance with the multivariate analysis at the time of determining parameters of the expression. On the other hand, the latter deterministic technique is one in which, considering that the radio wave radiated from an antenna is a collection of a number of radio wave rays, each ray is reflected and transmitted repeatedly on the geometrical optics, and propagated, and the rays incoming to an observation point is synthesized to obtain the propagation loss and the amount of delay.
This technique of geometrical optics is further classified into an imaging technique and a ray launching technique. The imaging technique determines a reflection and transmission path of the ray connecting between the transmitting and receiving points by obtaining an imaging point against the reflection surface. Since the reflection and transmission path is uniquely determined if the transmitting and receiving points and the reflecting and transmitting objects are defined, the imaging technique is one of searching for a strict propagation route of the ray. On the other hand, the ray launching technique is one in which the rays from an antenna are radiated to predetermined directions, irrespective of the receiving point, and the ray passing near the receiving point through the repeated reflection and transmission is regarded as the ray incoming to the receiving point. This was described in Japanese Patent Laid-Open No. 9-33584 specification, for example.
The ray launching technique solves approximately, but not strictly like the imaging technique, the propagation route of the ray connecting between the transmitting and receiving points, and has a feature of shortening the time needed to search for the propagation route.
FIG. 13 is a view for explaining the operation of the ray launching technique in the case where an observation area 020, a transmitting point 009, a receiving point 010, and two contents 001 and 002 within the observation area are provided. In FIG. 13, for the simplicity, the operation is explained only in the two dimensional plane, but practically, the operation may be performed in the three dimensional space.
First of all, a ray is radiated from the transmitting point 009 in a direction toward the propagation route 003. With regard to all the contents within the observation area, it is determined whether or not the ray radiated in that direction strikes the contents existing within the observation area. The ray strikes a content 001 at a reflection point 012 to generate a transmitted ray 011 and a reflected ray 004. The ray 004 produced by reflection further strikes a content 002 to generate a transmitted ray 013 and a reflected ray 008 in similar manner. The reflected ray 008, which passes in the vicinity of the receiving point 010, is regarded as the incoming wave in the observation point.
Specifically, the propagation routes 003, 004 and 008, the receiving strength as defined from a total of propagation distances and the incoming delay time are recorded in FIG. 14. In FIG. 14, the transverse axis 101 represents the delay time required for the ray to arrive from the transmitting point 009 via the routes 003, 004 and 008 to the observation point 010, and the longitudinal axis 102 represents the received electric-field strength of the ray passing through the route.
The ray from the transmitting point 009 in the direction toward the propagation route 003 has the transmitted rays 011 and 013, for which the transmission and reflection are repeatedly searched, as in the propagation routes 003, 004 and 008, wherein the ray passing in the vicinity of the receiving point 010 is treated as the incoming wave, as in the propagation route 008, and the above processing is continued till the search end condition is met. The search end condition is that the received field strength at the reflection and transmission point falls below a predetermined value. In this invention, the above process is called the ray launching processing.
After the ray radiated from the transmitting point 009 in the direction toward the propagation route 003 is searched for the reflection and transmission, the same ray launching processing is made by changing the radiation angle of the ray radiated from the transmitting point 009, as in a route 006, for example, and investigating all the radiation directions from the transmitting point 009, or partial radiation directions as defined beforehand. Lastly, FIG. 15 which shows a delay profile for the receiving point 010 is obtained. In FIG. 15, the transverse axis 201 represents the delay time when the ray comes in from the transmitting point 009, and the longitudinal axis 202 represents the received electric-field strength of the ray passing through the route. The received power at the receiving point 010 is given by a total of received strength for all the paths as indicated in FIG. 15, and the delay spreading for indicating degrees of the distortion is given by the standard deviation of the delay time.
The ray launching technique that gives a solution of the propagation route of the ray connecting the transmitting and receiving points approximately, but not strictly as by the imaging technique, takes a shorter time for searching the propagation route than the imaging method. However, it still takes a lot of time in the case where there is a large building or there are a very great number of fixtures (e.g., contents 001 and 002 in FIG. 13) installed within the building.
It is an object of the present invention to provide a system and method for predicting the radio wave propagation characteristics in which the ray launching technique is performed at higher speed, employing a parallel computer, and a recording medium for recording a program for use with the method.
According to the present invention, there is provided a system for predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the system comprising a plurality of CPUs (Central Processing Units) that are interconnected via a network, wherein the plural rays radiated from the transmitting point are divided into a plurality of groups, each group being allocated to a different CPU, and the ray launching processing is performed for all the allocated rays independently and simultaneously by the plurality of CPUs.
According to the present invention, there is provided a system for predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the system comprising a plurality of CPUs (Central Processing Units) that are interconnected via a network, and a recording device that can be accessed from each of all the CPUs, wherein each of the plural rays radiated from the transmitting point has a respective priority set, each of the CPUs is assigned one ray in the order of higher priority, and the ray launching processing is performed for the assigned rays simultaneously by the plurality of CPUs, wherein the ray with the next priority that has not yet been assigned to the CPU is selected in the order of the CPUs that have ended the ray launching processing, the CPU performing the ray launching processing for the selected ray, and an indicator for indicating that the selected ray is processed by the CPU is recorded into the recording device, and wherein a ray selecting process of selecting the ray by referring to the recording device and the ray launching processing are repeatedly performed until the last ray is reached.
According to the present invention, there is provided a system for predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the system comprising a plurality of CPUs (Central Processing Units) that are interconnected via a network, a recording device that can be accessed from all the CPUs, and a priority table set up for each of the CPUs and indicating a priority of each of the plural rays radiated from the transmitting point, the priority table being different for each of the CPUs, wherein the ray having the highest priority is selected from among the rays for which the lay launching processing has not yet been performed by the CPUs by referring to the priority table provided for each of the CPUs, and each of the CPU performs the lay launching processing for the selected ray, in which the ray launching processing is performed simultaneously by all the CPUs, wherein each of the CPUs records an indicator for indicating that the ray launching processing is performed for the ray in the recording device, and each of the CPUs grasps whether or not the ray launching processing has been performed for a certain ray by referring to the recording device, and wherein each of the CPUs performs repetitively a ray assignment processing and the ray launching processing for the ray until the last ray is reached.
The priority of the ray having a longer processing time for the ray launching processing is set to be higher in the CPU of greater processing capability and lower in the CPU of smaller processing capability.
To detect a shield shielding a ray among a plurality of contents in the ray launching processing, each of the CPUs comprising first image acquiring means for acquiring a first image of the ray projected onto a projected object preset within the observation space, second image acquiring means for acquiring a second image of each of the contents projected onto the projected object, determination means for determining whether or not the first image and the second image intersect each other, and detection object concluding means for concluding a corresponding content as the shield detection object for the ray, in the case where the result of determination indicates the intersection.
Each of the CPUs further includes control means for controlling the execution of the first image acquiring means, the second image acquiring means, the determination means and the detection object concluding means, such that the M projected objects (M is an integer of 2 or greater) are set up, the first image acquiring means, the second image acquiring means, the determination means and the detection object concluding means are controlled for execution for a projected object i=1 (i is from 1 to M), then for a content concluded by the detected object concluding means, the first image acquiring means, the second image acquiring means, the determination means and the detection object concluding means are controlled for execution for a projected object i=2, and the same control for execution is repeated till a projected object i=M.
Further, to detect a shield shielding a ray among a plurality of contents in the ray launching processing, each of the CPUs comprising means for acquiring an image A of the ray projected onto a projected object i, in which a plurality of projected objects i (i=1 to M: M is an integer of 2 or greater) are set up within the observation space, a group k (k=0 to M) representing part or all of the contents is defined, and a group o is a set of all the contents as defined within the observation space, means for selecting one content from the group ixe2x88x921 and acquiring an image B of the content projected onto the projected object i, means for practicing a selectively incorporating process by checking whether or not the images A and B intersect, and selectively incorporating the content into the group i if the images A and B intersect, means for practicing the selectively incorporating process of the contents included in the group i by practicing the selectively incorporating process for each of all other contents in the group ixe2x88x921, and means for detecting the shield for the contents included in a group M and concluded ultimately by practicing the selectively incorporating process of the contents for i=1 to M in sequence.
Supposing that the projected object i is a line or a plane as defined in the three dimensional space, different lines or planes are assigned to the projected objects. Also, the line is assigned to each of the projected objects i=1 to L (L is an integer such as 2xe2x89xa6L less than M), and the plane is assigned to each of the projected objects i=L+1 to M. The projected object i is set at a smaller value as the length of the ray projected onto the projected object is smaller.
Furthermore, supposing that the absolute value of an elevation angle of the ray with respect to a predetermined plane is t, and the absolute value of an elevation angle of the projected object with respect to the predetermined plane is T, the projected object is variably set in accordance with the value of t, and the projected object i is set such that there is a greater difference between t and T for smaller i.
According to the present invention, there is provided a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the method comprising dividing the plural rays radiated from the transmitting point into a plurality of groups, and allocating each group to a different CPU, and performing the ray launching processing for all the allocated rays independently and simultaneously by the plurality of CPUs.
According to the present invention, there is provided a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the method comprising setting the plural rays radiated from the transmitting point with respective priorities, and assigning each of the CPUs with one ray in the order of higher priority, performing the ray launching processing for the assigned rays simultaneously by the plurality of CPUs, selecting the ray with the next priority that has not been assigned to the CPU in the order of the CPUs that have ended the ray launching processing, each of the CPUs performing the ray launching processing for the selected ray, and recording an indicator for indicating that the selected ray is processed in the CPU into the recording device, in which a ray selecting process for selecting the ray by referring to the recording device and the ray launching processing are repeatedly performed until the last ray is reached.
According to the present invention, there is provided a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the method comprising setting up a priority table for each of the CPUs and indicating a priority of each of the plural rays radiated from the transmitting point, the priority table being different for each of the CPUs, selecting the ray having the highest priority from among the rays for which the lay launching processing has not yet been performed by the CPUs by referring to the priority table provided for each of the CPUs, each of the CPUs performing the lay launching processing for the selected ray, in which the ray launching processing is simultaneously by all the CPUs, each of the CPUs recording an indicator for indicating that the ray launching processing is performed for the ray into the recording device, and each of the CPUs grasping whether or not the ray launching processing has been performed for a certain ray by referring to the recording device, in which each of the CPUs performs repetitively an assignment processing and the ray launching processing for the ray until the last ray is reached.
To detect a shield shielding a ray among a plurality of contents in the ray launching processing, the method comprising, in each of the CPUs, a first step of acquiring a first image of the ray projected onto a projected object preset within the observation space, a second step of acquiring a second image of each of the contents projected onto the projected object, a third step of determining whether or not the first image and the second image intersect each other, and a fourth step of concluding a corresponding content as the shield detection object for the ray, in the case where the result of determination indicates the intersection.
Also, the M projected objects (M is an integer of 2 or greater) are set up, the first to fourth steps are executed for a projected object i=1 (i is from 1 to M), then for a content concluded at the fourth step, the first to fourth steps are executed for a projected object i=2, and the same processing is repeated till a projected object i=M.
Furthermore, to detect a shield shielding a ray among a plurality of contents in the ray launching processing, the method comprising, in each of the CPUs, a step of acquiring an image A of the ray projected onto a projected object i, in which a plurality of projected objects i (i=1 to M: M is an integer of 2 or greater) are set up within the observation space, a group k (k=0 to M) representing part or all of the contents is defined, and a group o is a set of all the contents as defined within the observation space, a step of selecting one content from the group ixe2x88x921 and acquiring an image B of the content projected onto the projected object i, a step of practicing a selectively incorporating process by checking whether or not the images A and B intersect, and selectively incorporating the content into the group i if the images A and B intersect, a step of practicing the selectively incorporating process of the contents included in the group i by practicing the selectively incorporating process for each of all other contents in the group ixe2x88x921, and a step of detecting the shield for the contents included in a group M and concluded ultimately by practicing the selectively incorporating process of the contents for i=1 to M in sequence.
Also, supposing that the projected object i is a line or a plane as defined in the three dimensional space, different lines or planes are assigned to the projected objects. Also, the line is assigned to each of the projected objects i=1 to L (L is an integer such as 2xe2x89xa6L less than M), and the plane is assigned to each of the projected objects i=L+1 to M. Moreover, the projected object i is set at a smaller value as the length of the ray projected onto the projected object is smaller. Also, supposing that the absolute value of an elevation angle of the ray with respect to a predetermined plane is t, and the absolute value of an elevation angle of the projected object with respect to the predetermined plane is T, the projected object is variably set in accordance with the value of t, and the projected object i is set such that there is a greater difference between t and T for smaller i.
According to the present invention, there is provided a recording medium for recording a program for enabling a computer to execute a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the program comprising a step of dividing the plural rays radiated from the transmitting point into a plurality of groups, and allocating each group to a different CPU, and a step of performing the ray launching processing for all the allocated rays independently and simultaneously by the plurality of CPUs.
According to the present invention, there is provided a recording medium for recording a program for enabling a computer to execute a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the program comprising a step of setting the plural rays radiated from the transmitting point with respective priorities, and assigning each of the CPUs with one ray in the order of higher priority, a step of performing the ray launching processing for the assigned rays simultaneously by the plurality of CPUs, a step of selecting the ray with the next priority that has not yet been assigned to the CPU in the order of the CPUs that have ended the ray launching processing, each of the CPUs performing the ray launching processing for the selected ray, and a step of recording an indicator for indicating that the selected ray is processed by the CPU into the recording device, in which a ray selecting process for selecting the ray by referring to the recording device and the ray launching processing are repeatedly performed until the last ray is reached.
According to the present invention, there is provided a recording medium for recording a program for enabling a computer to execute a method of predicting the radio wave propagation characteristics in which a plurality of contents, a transmitting point and a receiving point are provided in an observation space as defined within a three dimensional space, and the plural radio wave rays are radiated at different angles from the transmitting point over the observation space, the rays being reflected or transmitted repetitively upon the collision with the plurality of contents as the rays proceed, and in which a ray launching processing for acquiring the information of the passage time and the intensity of the ray at the time of passing in the vicinity of the receiving point is performed while the ray is being reflected or transmitted repetitively, the program comprising a step of setting up a priority table for each of the CPUs and indicating a priority of each of the plural rays radiated from the transmitting point, the priority table being different for each of the CPUs, a step of selecting a ray having the highest priority from among the rays for which the lay launching processing has not yet been performed by a self CPU and the other CPUs by referring to the priority table provided for each of the CPUs, each of the CPUs performing the lay launching processing for the selected ray, and a step of performing the ray launching processing simultaneously by all the CPUs, each of the CPUs recording an indicator for indicating that the ray launching processing is performed for the ray in the recording device, and a step of grasping whether or not the ray launching processing has been performed for a certain ray by referring to the recording device in each of the CPUs, whereby each of the CPUs performs repetitively the assignment processing and the ray launching processing for the ray until the last ray is reached.
The operation of the present invention will be set forth below. The ray launching processing for the plural rays radiated from the predetermined transmitting point is configured so as to be performed simultaneously and in parallel by the plurality of CPUs, in such a way as to divide the plural rays radiated from the transmitting point and allocating one ray to each of the CPUs, resulting in a shorter computation time.